The present invention is directed to switching regulator apparatuses, and especially to switching regulator apparatuses with outputs precharged substantially equal with or less than the rated output signal level of the regulator apparatus.
In certain applications in which switching regulator apparatuses are employed the output voltage of the regulator is precharged to a voltage greater than zero but less than the target or rated output voltage. In a typical situation involving startup of switching regulators, the output of the regulator apparatus operates according to a soft start voltage that increases from zero to a level desired for output regulation, i.e., the regulated or rated output voltage. Output loci at which the output voltage is presented by the apparatus are sometimes required to be precharged in order to meet certain specifications of devices using the regulator apparatus. One example of such a requirement of a precharging of an output locus of a switching regulator is when such a regulator is employed in providing power sequencing for a DSP (Digital Signal Processor) device. Soft start voltages and precharged output loci are used in startup sequences for such devices to preclude damage to the DSP.
If the output locus is precharged, or prebiased, to a voltage greater than zero but less than the rated output voltage, then during startup of the regulator a large current may flow from the output locus through at least a portion of the regulator apparatus. Such a xe2x80x9creverse current flowxe2x80x9d into and through at least a portion of the regulator may damage internal components within the regulator. Such a xe2x80x9creverse current flowxe2x80x9d may also be described as current sinking to the regulator. The resultant damage may render the regulator inoperative, or may contribute to decreased reliability in future operation of the regulator. Likelihood of decreased reliability is exacerbated if the regulator is subjected to repeated instances of such current sinking.
There is a need for an apparatus and method for controlling startup of a precharged switching regulator that precludes current sinking to the regulator.
An apparatus for presenting a regulated output at an output locus established at a precharge level includes: (a) an error indicator generating an error signal indicating difference between a reference signal and a sensed signal; (b) a pulse indicator coupled with the error indicator generating a pulse signal indicating difference between the error signal and a periodic signal; (c) a switching device responding to the pulse signal effecting coupling of the output locus with a first terminal or a second terminal depending upon whether the pulse signal is at a first level or a second level; and (d) a driver controller coupled with the pulse indicator and the switching device that provides a control signal to the switching device indicating at least one characteristic of the pulse signal. The switching device is operative or inoperative depending upon whether the control signal is in a first state or a second state.
A method for controlling startup of a precharged switching regulator apparatus includes the steps of: (A) In no particular order, (1) Providing a switched regulator apparatus configured for presenting a substantially regulated output signal at an output locus. The output locus is established at a precharge level less than the regulated output signal. The switched regulator apparatus includes: [a] an error indicator device that generates an error signal indicating a first difference between a reference signal and a sensed signal; [b] a pulse indicator device coupled with the error indicator device and generating a pulse signal indicating a second difference between the error signal and a periodic reference signal; and [c] a switching device coupled with the pulse indicator device and responding to the pulse signal to effect switched coupling of the output locus with a first terminal when the pulse signal is at a first signal level, and to effect switched coupling of the output locus with a second terminal when the pulse signal is at a second signal level. (2) Providing a driver control device coupled with the pulse indicator device and the switching device. The driver control device provides a control signal to the switching device indicating at least one characteristic of the pulse signal. The switching device responds to the control signal. The switching device is in an inoperative condition when the control signal is in a first state and is in an operative condition when the control signal is in a second state. (3) Establishing the control signal in the first state to place the switching device in the inoperative state. The method includes the further steps of: (B) Commencing a startup sequence for the apparatus. (C) Sampling the pulse signal. (D) Determining whether a pulse signal is extant. (E) If no pulse signal is extant, repeating steps (C) through (D). (F) If a pulse signal is extant, determining whether a predetermined criteria has been met. (G) If the predetermined criteria has not been met, repeating steps (C) through (F). (H) If the predetermined criteria has been met, establishing the control signal in the second state to place the switching device in the operative state. (I) Terminating the startup sequence.
It is, therefore, an object of the present invention to provide an apparatus and method for controlling startup of a precharged switching regulator that precludes current sinking to the regulator.